Process of dislodging slime cakes from filter media.



G. BUTTERS. PROCESS OF DISLODGING SLIME CAKES FROM FILTER MEDIA. AfPLIOATION FILED JUNE13, 1913.

1,078,994, Patented Nov. 18, 1913.

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C. BUTTERS.

PROCESS OF DISLODGING SLIME CAKES FROM FILTER MEDIA.

APPLICATION FILED JUNE 13, 1913.

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G. BUTTERS. PROCESS OF DISLODGING SLIME CAKES FROM FILTER MEDIA.

APPLICATION FILED JUNE13,1013.

Patented Nov. 18, 1913.

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CHARLES BUTTERS, OF OAKLAND, CALIFORNIA.

PROCESS OF DISLODGING SLIME CAKES FROM FILTER MEDIA.

Specification of Letters Patent.

Patented Nov. 18, 1913.

Application filed June 13, 1913. Serial No. 773.375.

To a whom it may concern lle it known that 1, CHARLES B'u'r'rnns, a citizen of the United States, and a resident of Oakland. county of Alameda, State of (,alifornia, have invented new and useful Improvements in Processes of Dislodging Slime Cakes from Filter Media, of which the followingis a specification.

An object of my invention is the production of a filter loaf of low cost and simple construction which will permit of eeonomi cal filtering and satisfactory cake dislodgmentm ln abstracting the values from slimes one of the most diflicult and troublesome problems is to dislodge reliably and within an economical time, the slime cake from the surface of the filtering medium after the filtering process has been completed, without injuring the filtering surface of the leaf.

It has been the practice heretofore to dislodge slime cakes by air pressure placed on the interior of the leaves while suspended in the air, or this has been accomplished in some cases by water under pressure being passed through the filtering medium' in a direction reverse to hat of the filtrate. It

has been supposed heretofore that to ilis lodge the cake reliably and within an coonomical time, pressure was -"1'tecessai whether air. water, or other fluid was used in the dislodging step, and whether used interiorly or exteriorly. \Vhcn used interiorly special precaution has sometimes been taken to get a uniformly thick, cohesive and resistant cake deposit such that the fluid under pressure might: dislodge it as an entirety and make it um'iecessary to use additional means to dislodge the cake completely. By my process such, uniformity of the cake is of no importance at all to the cake dislodgment, and consequently the filtering operation may b more economical.

If notable internal pressure is put on a leaf for cake-dislodgment purposes, a heavy filtering medium is necessary and means must heprovided to prevent distention or ballooning of the filtering medium. Various means have been devised to this end, all of which have added to the difficulty of cakedislodgment. As a matter of practice, too, it is found that all such meansv are a bindrance to proper and economical operation; further, they shorten the life of the leaves,

but they have been regarded as indispensable when former practicable methods of cakedislodgrnicnt by internal pressure have been used.

The ellicicncy of the leaves heretofore used is low, first, because a considerable amount of the filtering.surface of the medium is obstructed by the means used to prevent ballooning. such as strips down the sides; and second. because of stitching the media together or by bolting strips onto the outside of the leaf to prevent ballooning, comparatively large holes are made in the media. Also, these holes ma kc the media more liable to rupture under internal pressure, thus shortening their life. A further cause of low efliciency in some types of leaves has been the filler for keeping the filtering media separated when suction is applied to the leaf. The types referred to are those using: a rigid non-porous filler with relatively lare'e surfaces contacting tightly with the media. 'lhese tightly contacting internal surfaces are a great hindrance to the flow of the filtrate and to the dislodgment of the cake. I therefore use a porous fibrous filler such as cocoa mat. It has also been proposed hcretofore to dislodge cakes by external sprays or Jets variously applied, but these have generally sought to direct the water under pressure against the cake, and

rely upon the mechanical action of the water. I have discovered that pressure is unnecessary when external water is used for dislodging the cake if the cake has been previouslv partially dried.

It is found in practice that slime cakes have unusual adhesion and cohesion and that when a cake is formed on each side of a-filter lea l they are not easily dislodged. The adhesion of the cakes depends in a measure upon the moisture contained in them. and t depends in a measure also upon the character of the filter leaf surface. I have discoverwl that from a comparatively smooth filter leaf surface the cake can be reliably and promptly dislodged if it is first partially d ricd, and is then copiously flooded externally.

By my process in its preferred form, the moisture of the cake is withdrawn as completely and rapidly as possible by maintaining the maximum possible vacuum within the leaf for a time While the leaf with the cake thereon is suspended in air. After the cake is thus dried water'is flooded down onto the cake while the vacuum is at the same time relieved, and the cake is thereby dislodged from the filtering surface in from one .to three minutes and the filtering surface is washed clean by the water from above.

I have, therefore, devised a leaf which is simple in construction which has a perfectly smooth surface, exce t for one or two spacers on each 'side wliich help to hold the cakes on the leaves'prior to the dislodging step; a comparatively light filter cloth; an which has means for supplying a large amount of water 'in a short time to the top of the cake when desired.

Other advantages will be apparent after reading the following detailed description, taken in connection with the accompanying drawings, which form a fication, and in which- Figure 1' is a plan view of the vats for containing the leaves and the vacuum and water supply pumps with their pipe con-- nections; Fig. 2 is an elevation of the devices shown m Fig. 1; Fig. 3 is a plan view of a vat with several leaves therein; Fig. 4 is a side elevation of a leaf embodying my invention; and Fig. 5 is a section on line 5-5 of Fig. 4.

In Fig. 1 are shown vats 1 in which the slimes bath to be treated is contained and in which the leaves 2 are placed, as shown in Fig. 3. The contents of the vats may be discharged into the runway 32 by any suitable means. The leaf shown in Fig. 4 consists of headers 12. (which support the leaf on shoulders 31 of the vats), a fibrous filler 13, preferably of cocoa mat, and 'a filtering medium 14, such as canvas, mounted on each side of a frame and the cocoa mat. The medium may be composed of two separate pieces sewed along the sides and clamped at the to between the headers 12, or it may be a singe piece sewed on the sides, clamped at v the top between the headers and open acro'ss the bottom. The open portions extend a shortdistance below the frame member 15, say six or eight inches. The extended open portion of the medium 14 may be stitched every nine or ten inches as shown. These stitches hold the extended portions of the medium in place particularly when the leaf is being placed in the slimes either by lowering t e leaf in the slimes or running the slimes into the-vat around the leaf. The open portions will be closed-when vacuum is turned on .the leaf.

The type of leaf shownis preferred, although other types may be used. It is foundin practice that by the use of a leaf of'thenjparticular tyipe shown, the cake is more dasily dislodge and there is less trouble frond hme deposit.

part of this speci-' The connections 4 communicate with the interior of the leaves through the frame members 8, 9 and 11. The lower frame member 9 is perforated or slotted along its upper side in the well known manner. The upper frame member 11' is perforated. or slotted along its lower side. Whenthe vacuum pump is started suction is producedjim side the leaf through-both the upper-member 11 and the lower member 9. A vacuum pump 3 is connected with the interior of" theleaves through the pipe 7, valves 6, sight. glasses 5, connections 4 and members 8 and perforated members 9 and 11. The frame members 8, 9, 10 and 11 are connected together so as to form a rigid framestructure and are all in open communication with one another. The member '10 extends up, ward through the headers 12 to a T joint 16. Placed in this extension above the header is a plug 19 to seal the vacuum tliei e and also to prevent the entrance of water from the pipe 26 into the leaf. The headers 12, which are steel members, are bent so as to allow the pipe 10 to pass between them.

In order that the leaves may be properly'and easily put'in position in the vat, strips or spacers 27 are put on the-sides ofthe leaf and are held in lace by passing bolts 28 through them. T ese spacers also add some friction surface to the leaf and help to hold the cakes thereon when they are removed from the bath.

A pipe 15, perforated along its lower side (for example with inch holes 3 inches apart,) is supported well above the headers 12 of each leaf (and above the top of the slimes bath in the vat and so above the top of the cake on the filter lea-f) by means of supports, such as straps 17. These straps may be of suitable material bolted through the headers by means of bolts 18, The straps 17 may bend immediately around the pipe and have a bolt 21 passing through the straps below the pipe. For the purpose of removing the leaves from thevats, holes 20 are provided in the headers 12 in which suit-' able hooks may be inserted for lifting the leaf. Connected with the pipe 15 is a pressure pump 22. The pump/is connected with the pipe '15 through the valve 23; pipe-2st, j

valves. 25 and connections" 26. By means of the pump and the above connections wa ter may be forced at any desired pressure, "as

say 60 pounds, through the pipe 15 and directed on top of the headers 12. The header will take the pressure of the water rather than the cake, and the water will-'merely run down copiously over the 'leaf and its at:

tached cake without any substantial gp res sure. The purpose of the pump22, ;its 'connections and the pipe15 is to delivera lar e amount of water on top of theheader wittin a very short time.

Theoperation of my process and apparatus is as follows: The leaves are submerged in the slimes to be treated, vacuum is created within the leaf by the vacuum pump 3, and this is continued until a cake of proper thickness is deposited on the filtering media! As soon as vacuum is turned on and as long as it is maintained the extended portions of the media close and seal. If it is desired, the cake is then treated with barren solution and wash water in the usual way, the vacuum being maintained continuously. -When the cake has been suitably treated and washed, the leaf, with its cake, will be removed from the wash water either by lifting the cake into the air or by decanting the water from the vat, while still maintaining, the vacuum on the leaf. When the cake is out of the wash water and is suspended in the air, the full vacuum will be maintained for about five to ten minutes. This will entirely empty the leaf of water and will rapidly remove a considerable portion of the contained moisture from the cake and so approximately dry the cake. The vacuum pump is then cut off and water is admitted under conside able pressure into the pipe 15 and through the perforations therein onto the top of the header 12, flooding the entire upper portion of the leaf and cake. The cake is dislodged in from one to three minutes and the filtering surface is washed clean by the am from the. one-quarter inch holes in the pipe 15. The cake drops into the hopper-shaped bottom of the vats and may be sluiced away. s

The cake at the end of the filtering process and before the special drying step contains about 30% of moisture. By the special drying step, namely, the described full vacuum action of the pump for about five to ten minutes while the cake is suspended in air, the moisture contained at the end of the filterin process is reduced to about 20% and may bemore or less-concentrated toward the inner parts of the cake. The special drying action described seems to tend to crack the cake at the top and to more or less initiate there a separation of the cake from the filtering medium. And when at the end of the special drying step the vacuum pump is cut off the cake seems to sag at the top and to start to dislodge itself by its own weight from the filter medium there, and the copious flood of water applied then and there as the cake separates from the cloth seems to hasten and insure the dislodgment. The dislodging process per .90, therefore, consists broadly in approximately drying the cake after the filtering process is over and then copiously flooding the cake.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. The method of dislodging cakes from filter leaves, which ponsists in approximately drying said cakes and subsequently flooding them.

2. The method of dislodging cakes from filter leaves, which consists in approximately drying said cakes and subsequently flooding them from above.

3. The method of dislodging slime cakes from tilter leaves, which consists in sucking said cakes approximately dry and then simultaneously ceasing the suction and flood ing the cakes with water.

4. The method of dislodging slime cakes from filter leaves, which consists in sucking said 'akes approximately dry and then simultaneously ceasin r the suction and flooding the top of the ca es with water.

The method of dislodging slime cakes from filter leaves, which consists in approximately drying the cakes by vacuum, relieving the vacuum and immediately flooding the cakes with water.

(i. The method of (lislodging slime cakes from filter leaves, which consists in approximately drying the cakes by vacuum, relieving the vacuum and immediately flooding the top of the cakes with water.

7. The method of dislodging a slime cake from a filtering surface, which consists in sucking moisture from the cake to approximately dry it and subsequently flooding the cake and the filtering surface with water along the upper line of adhesion of the cake to the surface.

8. The )l'ocess of dislodging a slime cake from a ti tering surface, which consists in reducing the moisture contained in the cake to substantially 20% and then at once flooding the cake exteriorly with water.

9. The method of dislodging a slime cake from a filtering surface, which consists in removing approximately onethird of its contained moisture and then at once flooding it extcriorly with water.

10. The method of dislodging a slime cake from a filtering surface, which consists in sucking the moisture contained in the cake through the filtering surface on which it is carried until the cake is approximately dry and then at once flooding the cake with water.

11. The method of dislodging slime cakes from the filtering surfaces of a filter leaf, which consists in continuing the vacuum within the leaf for approximately five minutes or more while the leaf and its cakes are in air, then relieving the vacuum and at once flooding the cakes with water.

12. The method of dislodging slime cakes from the filtering surfaces of a filter leaf, which consists in continuing the vacuum within the leaf for approximately five minutes or more while the leaf and its cakes are in air, and then simultaneously relieving the vacuum and flooding the cakes with water.

13. The method of dislodging slime cakes iro from the filtering surfaces of a filter leaf, testimony whereof, I have signed my Whlch consists in continuing the vacuum name tQthis specificatlon, in the presence of Within the leaf for approximately fix e m1n two subscribing wltnesses.

utes or more Whil the leaf and its cakes are CHARLES BUTTERS. 5 in air, and subsequently simultaneously re- .Wit-nesses: lieving the vacuum and flooding the upper NEWTON A. BURGESS,

portion of the leaf and cakes with Water. EDWIN SEGER.

Copies of this patent may be obtained for five cents each, by addressing the commissioner of Patents,

' Washington, D. C. 

